Graphene is a two-dimensional (2-D) material that has been attracting extensive scientific interest. The existence of single-layer graphene was not considered possible until recently when graphene was made from highly ordered pyrolytic graphite (HOPG) through mechanical cleavage. Since then, the extraordinary electronic properties of graphene, such as ballistic transport over ˜0.4 μm length, high electron mobility, quantum-hall effect at room temperature, and single-molecule field-effect sensitivity, have been experimentally observed. Semiconducting graphene nanoribbons have also been fabricated to demonstrate the high performance of graphene field-effect transistors. However, to make electronic devices from graphene, graphene needs to be placed on a substrate. Unfortunately, prior art methods of creating graphene do not provide an efficient and effective way of providing graphene on a substrate surface.
As mentioned above, one prior art method of creating graphene is through mechanical cleavage, also referred to as mechanical exfoliation. To provide graphene through mechanical exfoliation, graphene is peeled-off or rubbed off bulk graphite and transferred onto oxide substrates. This prior art method produces a very low yield of graphene and has no way of controlling the number of layers in the graphene. Other prior art synthetic methods may create the graphene through sublimation or liquid solution phase exfoliation and then deposit the film onto a substrate surface. However, sublimation requires temperatures in excess of 1300° C. and liquid solution phase exfoliation produces graphene with poor electrical properties due to the chemical processes required to form the graphene. These prior art synthetic methods also produce graphene with small domain sizes and it is difficult to control the number of layers in the graphene. Furthermore, the graphene still has to be transferred onto the target substrate.
Another growth method that has shown some promise is a chemical vapor deposition (CVD) method in which a solid metal, such as Nickel (Ni) or Copper (Cu), is placed in contact with a carbon source. As the metal cools, graphene is precipitated out of or grows on the metal. This prior art method provides larger areas of graphene and allows for good control of the number of layers of graphene. However, as with all of the other synthesis methods, transferring the graphene onto the substrate is an expensive, complicated and dirty process.